Those are zinc blisters, there may have been a bubble or a break in the copper plating, and the zinc core of the coin is beginning to corrode in that spot.
In 1982 the mint started to add zinc to some of one cent pieces and continue today. So these blisters or bubbles will be seen occasionally. Keep an eye out for the 1982d small date copper, that is very valuable.
and you may want to take a closer look at the mint mark... can't tell by the photos but to me it looks like there could be something different about it which is likely zinc rot as well, but if die markers match, could be a mm variety... check here https://www.coppercoins.com/advsearch.php just in case.
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